However, I also have a will

This is mostly focused on who Kaworu was, which involves those he associated most with. Instead of boring you with the usual story, personality, name information I think has been said enough times before, I'll bore you with his character through his interactions with other characters.

⇒ Introduction ; a bit of background for those who are new
⇒ Notes and Terms ; some vocabulary to familiarize
⇒ The Third Children ; the boy who fascinated him
⇒ The First Children ; similar, but not the same
⇒ Eva Unit 02 ; Asuka was amazing, but he's better

The reason I have existed

Kaworu's purpose and his destined fate, the ones which he choose not to follow, in the manga were very instrumental in SEELE's plan for humanity. But he really didn't care for any of it.

⇒ SEELE, the Throne of Souls ; the old men who controlled him
⇒ Adam, the first Angel ; his soul's origins, and sealed fate
⇒ Third Impact ; humanity's fate, and his reason for existing

Then kill me with that hand

Death was not a freedom, but a choice. This is not just about his end, but the meaning it carried, and the impact it left. A bit of randomness can be found here as well.

⇒ The final choice ; the only absolute liberty left
⇒ A reflection ; the impact he left behind
⇒ Doppelgangers ; other characters of interest